<!DOCTYPE html>
<html lang="en">
  <head>
      <meta charset="UTF-8">
      <title>组合选择器</title>
    <style type="text/css">
      /*
          组合选择器基本语法：
          选择器1, 选择器2, 选择器n {}
       */
      .class01, #id01 {
          width: 300px;
          height: 100px;
          border: 2px solid red;
      }
    </style>
  </head>

  <body>
    <div class="class01">lmy</div>
    <p id="id01">hello world</p>
  </body>
</html>